10 Bone-Headed Facts About Pachycephalosaurus

Pachycephalosaurus’ domed, heavily-built head looks like it was capable inflicting some serious damage. Unfortunately, trying to decipher how this animal used that noggin has given many poor scientists headaches of their own.

1. Its Skull Roof was Up to 10 Inches Thick.

Pachycephalosaurus heads only reached total lengths of two feet or so. In case you’re curious, human men and women have an average skull thickness of 6.5 and 7.1 millimeters, respectively.

2. Pachycephalosaurus Heads Were Once Mistaken for Dinosaur Kneecaps.

Dinosaurs—unlike mammals—lacked kneecaps altogether. However, during the late 19th century, this fact wasn’t widely known, and few non-skull-related Pachycephalosaurus bones had been found, so this weird hypothesis is pretty forgivable.

3. One of its Close Cousins Has the World’s Longest Dinosaur Name.

Try saying this five times fast: Micropachycephalosaurus. It means “small, thick-headed lizard.” What a flattering label!

4. Pachycephalosaurus May Have Drastically Changed Shape with Age.

Dr. John R. “Jack” Horner—who, among other accomplishments, served as the Jurassic Park trilogy’s dino consultant—maintains that Pachycephalosaurus and two similar creatures which shared its habitat were really the same animal. Stygimoloch and Dracorex are smaller and had much flatter skulls. If Horner’s correct, these represent two juvenile stages of Pachycephalosaurus. He expands upon his argument at the 8:30-mark of this TED clip:

5. It Belongs to the Same Dinosaur Clade as Triceratops.

Triceratops and its horned/frilled kin are collectively known as “ceratopsians.” Together with the pachycephalosaurids, they form a diverse dinosaurian group called the marginocephalia (“ridged heads”).

6. Perhaps Pachycephalosaurus Butted Heads.

Paleo-artists have traditionally drawn Pachycephalosaurus ramming headlong into each other musk ox-style. Does the available evidence support this? Some scientists think so, claiming that their domes were well-equipped for absorbing such brutal impacts. Others, meanwhile, have their doubts.

Today’s giraffes violently slam their heads into rivals’ sides. Maybe Pachycephalosaurus behaved likewise. Many of its kin had conspicuously-wide ribcages, which could theoretically withstand this sort of abuse. Also, try making two bowling balls forcefully collide at point-blank range. You’ll notice that the spheres will only briefly connect before quickly sliding apart thanks to their curvature. Pachycephalosaurus domes were also quite rounded and potentially faced the same mechanical challenge. If so, “flanking” might’ve been a more effective undertaking when tempers flared.

8. Pachycephalosaurus Had to Worry About T. rex.

Tyrannosaurus and Pachycephalosaurus both dwelled in western North America during the late Cretaceous period around 65 million years ago. That thick head was therefore possibly employed as an anti-predator weapon.

In 2012, paleontologist Joseph Peterson subjected a Pachycephalosaurus skull to CT scanning and found numerous potential injury marks “clustered over the thickest region of the dome,” which—in his view—seemingly corresponded with the head-butting hypothesis.

10. Pachycephalosaurus is (Indirectly) Linked to the Harry Potter Series.

To honor its dragon-like appearance and a certain best-selling book series, one new pachycephalosaurid species was named Dracorex hogwartsia in 2006. Upon hearing the good news, J.K. Rowling proclaimed “[this] is easily the most unexpected honor to have come my way since the publishing of the Harry Potter books! I am absolutely thrilled to think that Hogwarts has made a small claw mark on the fascinating world of dinosaurs.” She also added that “I can’t help but visualizing [Dracorex] as a slightly less pyromaniac Hungarian Horntail.”

But don’t get too excited, Potter fans. Remember: Dracorex could simply be nothing more than a young Pachycephalosaurus, which would make the Hogwarts-themed moniker obsolete.